The present invention relates to a method for making a design reference or rule and an apparatus therefor, and more particularly to such a method used by a designer who establishes a design reference or rule by selecting an object in an existing design drawing, selecting and combining specifications thereof and establishing a condition of design references.
A conventional computer-aided design apparatus (hereinafter CAD apparatus) comprises a display for displaying a design object and an input device for generating coordinate data based on the pointing to a position on the display screen, and interactively processes by displaying point, line or characters at the position pointed to by the designer and storing the coordinate of that position and the displayed data into a memory. Such CAD apparatus is described in JP-A-59-45575 and U.S. Pat. No. 4,451,895. In another known interactive CAD apparatus, when design parameters such as position, shape and dimension of the design object are entered, they are composed with reference values of design parameters derived from design references or rules so that the design proceeds while the validity of the input value is checked. In this CAD apparatus, it is necessary to previously store the design references in the memory A portion of the design references accumulated and utilized in the particular technical fields, such as design references on layout design of plant piping are published in a "Piping Handbook, by Reno C. King et al., McGraw-Hill 1981. It teaches that when a design expert determines a design reference or rule, it is effective to refer to an existing design drawing and quote, indicate or describe items on position and specification of the design object. In order to implement this method in the CAD apparatus, it is necessary to allow interactive reference of the data of the design object in the design drawing for use as data for making the design references. In a CAD apparatus disclosed in JP-A-59-220867 and JP-A-59-66763, when part of a machine design drawing displayed on a display screen is selected, a part of the data base is searched and data such as a part specification and dimension are registered in a list in the data base, and it may be displayed on the display screen or used to make a more detailed manufacturing design drawing. By utilizing the CAD apparatus disclosed in those A-PA's, the part data for checking the design references can be rapidly retrieved while the designer watches the design drawing. However, since the designer cannot directly input to the design reference making process, the designer needs to input the design references by a separate device to store them in the data base.